Various types of machines may use a work implement to transfer material from a work site and load this material onto transport vehicles (e.g., trucks and railroad cars). These machines include excavators, wheel loaders, backhoes, and other material moving machines. The transport vehicles that are loaded by the machines may have a particular load capacity determined by a manufacturer's maximum load rating and/or other factors, such as, for example, weight restrictions for on-highway vehicles. To promote maximum utilization of the transport vehicles, it may be desirable to load each transport vehicle as close as possible to its load capacity. Overloading the transport vehicle, however, may have negative consequences. Particularly, placing too much weight on a transport vehicle can significantly increase maintenance costs for the transport vehicle or create costly delays if the excess material is removed prior to transport.
To monitor the weight of the material placed onto each transport vehicle, machine manufacturers have developed payload calculation systems. A payload calculation system may determine the weight of a material currently carried by the work implement (e.g., weight of material in an excavator bucket), as well as the total weight of a material loaded onto a transport vehicle during a particular cycle or time period. For improved productivity, the payload calculation system may determine the weight of a material carried by the machine and/or work implement while the machine and/or work implement is in motion (rather than performing static measurements).
One method for determining the mass moved by a work implement is disclosed in U.S. Pat. No. 6,518,519 (the '519 patent) issued to Crane, III et al. on Feb. 11, 2003. The '519 patent discloses a machine with a chassis, a cab coupled with the chassis, and a boom coupled with the cab. A first actuator is coupled with the boom and the cab, and moves the boom relative to the cab. The machine has a stick coupled with the boom, and a second actuator coupled with the stick and the boom that moves the stick relative to the boom. The machine also has a bucket operable to receive the payload. The bucket is coupled with the stick, and a third actuator is coupled with the bucket and the stick and moves the bucket relative to the stick.
Various sensing devices are used to determine a first joint angle of the boom relative to the cab, a second joint angle of the stick relative to the boom, a third joint angle of the bucket relative to the stick, a first actuator force exerted on the first actuator, a second actuator force exerted on the second actuator, and a third actuator force exerted on the third actuator. A plurality of physical characteristics of the machine are also determined by, for example, accessing a data-set in a memory. A processing device receives the signals from the sensing devices at least two instances in time and, using dynamic equations, determines the mass or weight of the bucket and any payload in it as a function of the received signals and the predetermined physical characteristics of the machine. In the dynamic equations, the location of the center of mass of the bucket is expressed in terms of the unknown parameters, however the location of the center of mass of both the stick and the boom (in a fixed xy coordinate system) are assumed as known terms. The determination of the mass/weight of the bucket and payload may be made while one or all of the boom, stick, and bucket is in motion.
Although machines of the prior art may determine the mass/weight of the payload while one or all of the boom, stick, and bucket is in motion, changes in the location of the center of mass of the linkages may create inaccuracies in the determined mass.
The disclosed machine system is directed to overcoming one or more of the problems set forth above.